<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
</head><body>
<a href = "http://www.abc.com/abc/2007-9-26/abc.htm">test1</a><br/>
<a href = "http://www.abc.com/abc/2008-11-26/abc.htm">test1</a><br/>
<a href = "http://www.abc.com/abc/2008-9-01/abc.htm">test1</a><br/>
<a href = "http://www.abc.com/abc/nodate/abc.htm">test1</a><br/><script type="text/javascript">
var aNum=[
0,1,2,3,4,5,6,7,8,9,'a','b','c','d','e','f','g',
'h','i','j','k','l','m','n','o','p','q','r','s',
't','u','v','w','x','y','z','A','B','C','D','E',
'F','Q','H','I','J','K','L','M','N','O','P','Q',
'R','S','T','U','V','W','X','Y','Z','_','+','-'
];
//阶乘函数
function jc(num)
{
var result = 1;
for(var i=1;i<=num;i++)
result *= i;
return result;
}
var ds=new Date();
var len = aNum.length;
var get = 4;//取几个
var tmp = 1;
for(var i=0;i<get;i++)
tmp *= (len-i);
var total = tmp / jc(get);
var de=new Date();alert("从"+len+"个数里面取"+get+"个数进行组合，共有组合数:"+total+"\n"
+"用时:"+(de-ds));</script>
</body>
</html>
取4个，677040，用时0 :)
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>排列组合</title>
<script type="text/javascript">
var aNum=[
0,1,2,3,4,5,6,7,8,9,'a','b','c','d','e','f','g',
'h','i','j','k','l','m','n','o','p','q','r','s',
't','u','v','w','x','y','z','A','B','C','D','E',
'F','Q','H','I','J','K','L','M','N','O','P','Q',
'R','S','T','U','V','W','X','Y','Z','_','+','-'
];function getA(nLen)
{
var i;
var a1 = 1;
var a2 = 1;
var aLen = aNum.length;
for(i = (aLen - nLen + 1);i <= aLen;i++) a1 *= i
for(i = 1;i <= nLen;i++) a2 *= i
return a1 / a2;
}
var ds = new Date();
var a = getA(4);
var de = new Date();
alert("共有排列数 :"+ a + "\n" + "用时:" + (de-ds));
</script>
</head>
<body>
</body>
</html>